The invention relates to an apparatus for printing e.g. fotographic images on sheet material.
Colour printing methods are particularly used aside from other image recording methods in the digital image production. However, the colour printers used therefor nowadays and based on inkjet technologies or colouring agent sublimation technologies are relatively slow, and reach a maximum print capacity of typically ca. 50 pictures per hour (based on a picture format of 10 cmxc3x9715 cm, for example). Although integrated systems, such as the Canon Hyperphoto System, have a higher capacity, they print on roll material and therefore offer only little formatting flexibility without subsequent cropping of the pictures. Individual sheets are inserted as a stack in common desktop printers, which requires an exchange of the stack of sheets upon a change in format. In order to reach a certain minimum capacity with currently available printers suited for the processing of sheet material, it is necessary to operate several printers of the same type in parallel. This on one hand causes considerable installation cost and on the other hand requires a relatively large mounting area.
It is now an object of the present invention to solve this problem and to correspondingly improve a printing apparatus in accordance with the prior art so that the printing apparatus has an increased printing capacity (productivity) on the one hand as opposed to common printing apparatuses and on the other hand can be adapted to changing demands in an easy and economical manner with respect to its productivity. Furthermore, the printing apparatus should require a mounting area which is substantially independent from its printing capacity.
According to the principle idea of the invention, the printing apparatus is built in a modular manner and consists of a more or less large number of modules stacked one on top of the other, each of the modules containing a complete printing mechanism with all required components, as well as a distribution system for distributing the queued printing jobs to the individual modules and if necessary to bring them together again or to sort them after printing.
With this module concept, the capacity parameters of the printing apparatus can be coordinated exactly with the needs of the user. It is also possible to subsequently increase the capacity of the apparatus through a later addition of further modules or to adapt the capacity to decreased demands through the removal of modules. A further advantage of the modular set-up of the printing apparatus in accordance with the invention is a high flexibility. For example, if one module fails, the total capacity of the apparatus is only reduced by the portion of the failed module but the function of the apparatus is retained as long as at least one module is functioning.
In accordance with a further important aspect of the invention, the modules are designed so that they can be easily joined together, i.e. they can be stacked one on top of the other, without having to carry out cabling or wiring. The connection of the individual modules with each other is carried out in accordance with a preferred embodiment through a bus system having corresponding connection and expansion interfaces, for example in form of plug-in connections. In a base module there is provided a central control unit which recognises the connected expansion modules through the bus system and configures itself. The central control unit divides the queued printing jobs independently between the available modules and hence achieves optimally short run times for each individual job.
If the modules are equipped with inkjet printing mechanisms, the ink reservoirs are only situated in the base module in accordance with a further important aspect of the invention, and they are common to all modules. The modules are provided with an additional hydraulic bus system, which connects each module with the ink reservoir on one hand and on the other hand facilitates a simple connection of the modules with each other by means of suitable hydraulic connection and expansion interfaces provided in each module, e.g. in form of plug-in pipe couplings.